Is there an ideal body temperature? New research

What constitutes an ideal average body temperature? Is it 36.6 degrees Celsius or maybe 37 degrees Celsius?

Recent research has shown that our body temperature is profoundly influenced by various factors and varies from person to person. Contrary to the common belief in a fixed ideal body temperature, this study suggests it is highly individualized.

Normal?

In the mid-19th century, German physician Carl Reinhold August Wunderlich embarked on a quest to determine the normal body temperature in humans. He rightly believed that an elevated temperature indicates an underlying condition rather than being a disease itself. Wunderlich compiled tables of average body temperatures and introduced their use at the Universitätsklinikum Tübingen hospital, where he served as director.

Wunderlich built on the work of French doctors who discovered that inflamed body areas had higher temperatures than the rest of the body. They found the average human body temperature to be 36.9 degrees Celsius (98.5 Fahrenheit) and sought to solidify this as a scientific and medical fact. Wunderlich used a 30 cm long thermometer, mainly measuring armpit temperature, to collect data from 25,000 patients, resulting in over a million measurements.

Average human body temperature: 37 degrees Celsius?

In 1868, Wunderlich published his findings, stating that the average human body temperature is 37 degrees Celsius (98.6 Fahrenheit). Over the years, additional information has contributed to our understanding, revealing that body temperature varies throughout the day, being lower in the morning and peaking around 6 o'clock in the evening. Additionally, differences in body temperature between men and women have been identified.

In the time since Wunderlich's discoveries, scientists observed a peculiar trend: A consistent decrease in average body temperature.

A 2017 UK study, analyzing over a quarter of a million temperature measurements from 35,000 patients, found that the average mouth temperature was 36.6 degrees Celsius. A study earlier this year showed that the average body temperature in the US has steadily decreased by about 0.02 degrees Celsius every decade since 1860.

New research has further complicated the picture, revealing significant variation in body temperatures among individuals. While this challenges the conventional notion of normal body temperature, it may lead to more precise and tailored temperature measurements for clinical purposes.

Scientists from Stanford Medical Center assessed the body temperature of 618,306 patients who visited Stanford between 2008 and 2017, with measurements taken from the mouth.

The study, focused on adults with typical body temperature, unearthed an unexpected finding that individuals with type 2 diabetes tend to have lower body temperatures. The research group employed a smart algorithm-based device to diagnose and categorize individuals based on their body temperature.

The study found that body temperature is influenced by age, sex, height, weight, and the time of day the measurement is taken. Women tend to have slightly higher temperatures than men. Moreover, as age increases, average body temperature tends to decrease, with slight increases observed with greater weight and height.

So, what constitutes a normal body temperature?

The most influential factor affecting body temperature is the time of day, with the lowest body temperature typically occurring early in the morning and reaching its highest point around 4 p.m.

Many people, including healthcare professionals, still consider 37 degrees Celsius as normal, explained one doctor. In reality, what's normal varies based on the individual and the circumstances, and it's uncommon for body temperature to hit 37 degrees.

Individual variability

On average, the "normal" temperature ranges from 36.3°C to 36.8°C, with an overall average of 36.6°C. However, due to individual variability, the research team has developed an online tool to help individuals determine where their temperature falls within this range.

While this study did not explore factors such as weather, menstrual cycles, and physical activity, which may affect temperature measurements, the researchers hope that personalized temperature measures will enhance patient care outcomes by detecting abnormal fevers or low body temperatures in certain individuals.